Incomplete tenders and missing information seem to be a known constant in public procurement, confronting contracting authorities with legal challenges and critically influencing the results of public purchasing. Faced with a non-conforming tender that cannot be accepted, a contracting authority must choose between two options: to reject the tender or to ask for correction of mistakes in the tender. Exceptionally, instead of the option to clarify, the requirement of proportionality may justify an obligation to do. Subject to a complex discretionary decision, making the choice between a rejection and a clarification has to follow the general principles of EU public procurement law and good administration as well as the national administrative law rules. This article looks at the topic with the help of examples from Estonian case-law. By analysing both the relevant procedural and substantial rules, we draw guidelines to assist navigating the legal maze of conflicting considerations that concern the correction of mistakes and clarification of ambiguities in public procurement tenders. Keywords: clarification of tender; correction of mistake in tender; principle of proportionality

Mari Ann Simovart, Dr Iur, associate professor at the School of Law, University of Tartu. For correspondence: . Marit Piirisaar, associate at law office COBALT, Estonia. For correspondence: .